GCSE Questions: Waves
Susan played a note on an electric keyboard. The frequency of the note was 440 Hz.
(a)
(i) What does a frequency of 440 Hz mean? [1 mark]
440 Hz means that 440 (sound) waves (or vibrations or oscillations) are produced in one second. 
(ii) The sound waves produced by the keyboard travel at a speed of 340 m/s. Calculate the wavelength of the note. Use the correct equation from the Physics Equations Sheet. Give your answer to three significant figures. [3 marks]
wavespeed = frequency x wavelength
v = fλ
340 = 440 x λ
λ = 340/440 = 0.773 m
(b) The diagram shows a microphone connected to a cathode ray oscilloscope (CRO). It is being used to detect the note produced by the keyboard.
The diagram below shows the trace produced by the sound wave on the CRO.
A second note, of a different wavelength, was then played on the keyboard.
The diagram below shows the trace on the CRO produced by the sound wave of that second note. The settings on the CRO were unchanged.
What two conclusions should be made about the second sound wave produced by the keyboard compared with the first sound wave? Give a reason for each conclusion. [4 marks]
The amplitude of the second wave is greater, therefore the note is louder and the frequency of the second wave is greater therefore the note is of higher pitch. (Or you could say that the period of the second wave is shorter than the period of the first wave meaning the pitch is higher).
(Total: 8 marks)
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